As a heat wave bakes large pockets of the United States this weekend, it is society’s most vulnerable who suffer most.

Take the unnamed 32-year-old Ace Air Conditioning of Louisiana worker who died while installing duct work on July 20, 2017. The man began to show signs of heat exhaustion while working in the attic of a modest home in Lake Charles, Louisiana. Less than an hour later, he collapsed and died.

The company was fined a few thousand dollars because it did not “furnish employment and a place of employment which were free from recognized hazards.”

Or take the watermelon picker in Five Points, California, who collapsed on the way to his vehicle after a six-hour shift in temperatures above 100 Fahrenheit. No one on the team got a break that day, according to a colleague, despite state labor laws. When the man was pronounced dead at he hospital, his body temperature was 109 Fahrenheit. The company was fined $25,750.

These are just two examples of what outdoor workers face when temperatures rise.

The heat wave gripping much of the country has already been blamed for six deaths. As global temperatures continue to rise and heat waves become more common and extreme, it is the poor, the elderly, laborers, and people with medical conditions who will be at the greatest risk.

People over 65 are among those with the greatest risk of heat-related deaths, followed by men who work in outdoor occupations, according to the Environmental Protection Agency.

“Any person can suffer from heat stress, regardless of age, sex, or health status,” the agency wrote in a 2016 report on heat-related illness. “Older adults and children, however, have a higher-than-average risk of becoming ill due to exposure to extreme heat. People working outdoors, the socially isolated and economically disadvantaged, those with chronic illnesses, and some communities of color are also especially vulnerable to heat.”

When a massive heat wave struck Chicago in July 1995, the city was ill prepared to deal with the crisis. That lack of preparation had deadly consequences: 739 people died, including Valerie Brown’s grandmother, Alberta.

“They put my grandma’s body in a refrigerated truck,” Brown told NBC News. “There is no death certificate. They just took her body away and put her in a mass grave.”

It wasn’t just the elderly who were hit hardest by the 1995 heat wave in Chicago, according to Judith Helfand, who directed a new documentary about the heat wave, Cooked: Survival by Zip Code.

“The people who died in 1995 were poor, and disproportionately black,” Helfand told NBC News.

“Racism kills people,” she added.

Research has shown that climate change and the resulting heat waves will hit large urban areas particularly hard, in part because the concrete, brick, steel, and glass these cities are built from creates “heat islands” that trap heat during the day then slowly release it overnight, preventing the city from cooling down once the sun sets.

That creates a dangerous situation for people like construction workers, the elderly, the poor, minorities, and the homeless, who tend to be concentrated in cities and may not have the resources to stay in air-conditioned buildings when temperatures soar.

Just three states have regulations in place to protect outdoor workers in extreme heat. The advocacy group Public Citizen launched a campaign last year to get the Occupational Safety and  Health Administration to put tighter rules in place to protect workers during heat waves.

Meanwhile, President Donald Trump has nominated Eugene Scalia — son of late Supreme Court Justice Antonin Scalia and a lifelong opponent of labor regulations — to head the Department of Labor, which oversees OSHA.